The desirability of molding products without having a resulting molded product that has a sprue has been known for some time. For instance this permits molding a product in its finished or nearly finished condition so that the sprue that is formed in normal molding does not need to be removed. Consequently, no time needs to be spent on removing the sprue which reduces the labor and time necessary to make the product. In a similar manner the benefits of molding of products without runners has also been known for some time. This permits parts to be molded without the need to remove and separate runners from the products. Again this results in a saving of labor and time in manufacturing the molded product. In addition, the possible waste of molding material associated with the runners has been eliminated.
Unfortunately, a number of problems are possible with runnerless and sprueless molding including drooling, freeze-off, leakage and high maintenance. In order to avoid these and other problems, it is necessary to use injection molding nozzles that are heated and keep the molding material at a proper temperature as it is being injected. Heating itself does not prevent these problems. However, the injection molding nozzle invention solves all of these problems that have been present with past molding nozzles.
This injection mo1ding nozzle permits rapid and efficient runnerless and sprueless molding operations by properly controlling the temperature of the molten material being injected through the nozzle during the molding operation. This temperature control is aided by the unique design of the interior of the nozzle that results in the formation of an insulating barrier of material within the nozzle. The injection molding nozzle also permits the exit orifice size to be readily changed and it is also possible to increase the exit hole size but keep the same exit area that is not possible with current molding nozzles.